A method and system for embedding signatures within visual images in both digital representation and print or film. A signature is inseparably embedded within the visible image, the signature persisting through image transforms that include resizing as well as conversion to print or film and back to digital form. Signature points are selected from among the pixels of an original image. The pixel values of the signature points and surrounding pixels are adjusted by an amount detectable by a digital scanner. The adjusted signature points form a digital signature which is stored for future identification of subject images derived from the image. In one embodiment, a signature is embedded within an image by locating relative extrema in the continuous space of pixel values and selecting the signature points from among the extrema. Preferably, the signature is redundantly embedded in the image such that any of the redundant representations can be used to identify the signature. Identification of a subject image includes ensuring that the subject image is normalized with respect to the original image or the signed image. Preferably, the normalized subject image is compared with the stored digital signature.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of embedding data in an image encoded as points, each point having a parameter value, the method comprising the steps of: randomly selecting first and second points corresponding to relative extrema; and altering the image by i. increasing the parameter value of the first point and of a first patch of points surrounding the first point and ii. decreasing the parameter value of the second point and of a second patch of points surrounding the second point, thereby embedding data in the image.
2. The method of claim 1 wherein the step of randomly selecting is performed programmatically.
3. The method of claim 1 wherein each of the first and second points corresponds to an electronically represented pixel.
4. The method of claim 1 wherein the parameter values of points in patches are changed such that the first and second points can be identified after subsequent image processing.
5. The method of claim 1 wherein the parameter values of points in patches are changed in order to reduce visual perceptibility.
6. The method of claim 1 wherein the parameter values of points in first patches are changed by a first amount and the parameter values of points in second patches are changed by a second amount.
7. The method of claim 1 wherein the parameter values of points in first patches are increased by a first amount and the parameter values of points in second patches are decreased by a second amount.
8. The method of claim 1 further comprising the step of associating each randomly selected point with a 5.times.5 block surrounding the point, thereby defining several patches in the image.
9. The method of claim 8 wherein the patches are far apart.
10. The method of claim 1 wherein the set comprises at least 50 random numbers.
11. The method of claim 1 wherein the image is monochrome.
12. The method of claim 1 wherein the image is color.
13. The method of claim 1 wherein the parameter is luminance.
14. The method of claim 1 wherein the parameter is chrominance.
15. The method of claim 1 wherein the step of altering the image comprises changing the parameter value of points belonging to at least one of the first and second patches by a subgroup amount associated with a subgroup to which each point in the at least one of the first and second patches belongs.
16. The method of claim 15 wherein each subgroup amount has a magnitude that depends on position within a patch.
17. An apparatus for embedding data in an image, the apparatus comprising: means for randomly selecting first and second points corresponding to relative extrema; means for creating an altered image by i. increasing the pixel parameter value of the first point and of a first patch of points surrounding the first point and ii. decreasing the pixel parameter value of the second point and of a second patch of points surrounding the second point, thereby embedding data in the image.
18. An image created by altering a host image comprised of points, each point having a parameter value, by randomly selecting first and second points corresponding to relative extrema, and increasing the parameter value the first point and decreasing the parameter value of the second point.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 2, 2000
October 23, 2001
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